Gearbox fault light on Car stuck in neutral won’t move.

Hi, I’ve owned this car since Tuesday Evening this week, 31/10/2017. Everything upto this evening has worked great. I went to take my daughter to work this evening and put my car into drive and I get a fixed light on saying gearbox fault. It stays in auto about half a second then returns itself to neutral even when gear selector in auto.ive tried putting car into reverse and auto again while engine running and car remains still in neutral. I’ve tried turning car off then on again and problem persists. Any ideas anyone.